Updated salt-git package with new features

feautures:
- during installation a salt system user is created
- Creation of '/etc/salt/master.d/' for enhanced configuration
- salt-master run under own user 'salt'
- salt-user.conf created to set salt-master up for using salt system user
- added logrotate config files in appropriate place
- added bash-completion config files in appropriate place.
- Check if salt-master/salt-minion is running when upgrading
  and use systemd reexec / reload accordingly
- Updated removal of salt package to remove 'cache' and 'log' dirs.
  and removal of salt system user.
- Made installation more verbose to communicate what happens.